Installation and process for automatic preparation of samples

ABSTRACT

The invention relates to an installation for the automatic preparation of specimens by liquid/solid extraction on a column.  
     This installation is characterized in that the extraction device comprises, on either side of the columns ( 3 ), a valve ( 4 ) controllable to switch one column ( 3 ) to the other to actuate one column ( 3 ) adapted to ensure the extraction function when another column ( 3 ) is in a non-operating condition, each switching valve ( 4 ) being connected to a controllable common direction reversing valve ( 5 ) arranged to impose one direction of circulation on the fluid in anyone of the columns ( 3 ) of the extraction device and to ensure its return to said valve ( 5 ) to distribute the treated fluid toward a circuit selectively either for its rejection or for its analysis.

[0001] The present invention relates to an installation and a processfor the automatic preparation of specimens for measurement by a suitablemeasuring system, such as a UV spectrometer, an infrared device, afluorimeter, a mass spectrometer or the like.

[0002] The invention is applicable more particularly to following theprocess of natural or processed waters eventually adapted forconsumption, adapted to contain pesticides or other organic pollutants.More and more severe rules concerning the permissible concentrationthresholds in drinking water have required industry to develop newentirely automated installations permitting particularly apre-concentration by liquid/solid extraction and a line analysis of theobtained concentrates. Certain installations thus developed have not metwith the desired success because of the cost of the analyses. Such isthe case with the system developed by the ZYMARCK company. Thisinstallation carries out a line concentration on an absorbent disk. Asingle measurement is carried out per disk. Once the measurement iscarried out, the single use absorbent disk is discarded. As a result,there is a high cost of analysis. Similarly, the installation developedby the SPARK company is a concentration installation using a highcartridge. This installation permits the line elution in the directionof loading of a specimen. There is no reconditioning of the cartridgewhich is used but once. Moreover, the fact of working at high pressuregives rise to increased cost of the elements necessary for production ofthe installation. Other companies, such as the HEWLETT PACKARD company,have however envisaged the operation of a low pressure installation. Inthe case of this installation, there is provided a carousel carryingseveral low pressure cartridges. This carousel, serving as a cartridgecarrier, connects each specimen to a new cartridge. The introduction ofthe specimen into the cartridge takes place by percolation. Elution andloading are carried out in the same direction. There again results asingle use of the cartridge. The fact of having a cartridge carrierhowever permits the use in an autonomous manner of such an installationfor a relatively long period of time. Finally, other documents such asU.S. Pat. Nos. 4,070,284, 4,500,432, EP 0 571 716, U.S. Pat. No.5,449,902, WO 99/65587 and U.S. Pat. No. 5,117,109 illustrate the priorart of the invention.

[0003] An object of the present invention is to provide an installationand process for the automatic preparation of specimens whose respectivedesigns permit on the one hand reducing the wear on the columns of theextraction device, thereby permitting their re-use for a large number oftimes under conditions of total repeatability, on the other hand tooperate in a completely automatic and autonomous manner over a longperiod of time.

[0004] Another object of the present invention is to provide aninstallation and a process whose designs permit working at low pressureso as to reduce the cost of production and use of such an installation.

[0005] Another object of the present invention is to provide aninstallation whose flexibility of use permits perfect control of theliquid/solid extraction thanks to the possibility of programming andconfiguring as required the different steps of the extraction process.

[0006] To this end, the invention has for its object an installation forthe automatic preparation of specimens, particularly for concentratescomprising organic materials dissolved in a liquid phase, for analysison a suitable measuring system such as a UV spectrometer, an infrareddevice, a fluorimeter, a mass spectrometer or the like, thisinstallation comprising

[0007] a) a device for taking a liquid specimen,

[0008] b) a distribution device comprising a preferably low pressurevalve capable of selecting either the specimen, or one of the differentsolvents or reagents needed for a liquid/solid extraction process,

[0009] c) a low pressure pump permitting supplying at the selected flowrate a liquid/solid extraction device,

[0010] d) a liquid/solid extraction device constituted by a plurality ofcolumns each comprising at least one adsorbent phase,

[0011] the installation being characterized in that the extractiondevice comprises, on each side of the column, a controllable valve forswitching from one column to another to place in action a column adaptedto ensure the extraction function when the other column is in anon-operating condition, each switching valve being connected to acommon direction reversing valve interposed between the low pressurevalve and the switching valves, this controllable direction reversingvalve being arranged to impose a direction of circulation of the fluidin any one of the columns of the extraction device and to ensure itsreturn to said valve to distribute the treated fluid toward a selectivecircuit either for rejection or for analysis.

[0012] Thanks to the design of the installation, which permits on theone hand automatic switching from one column to the other, on the otherhand a regeneration of the column after each analysis thanks to abi-directional circulation and at low pressure of the fluids in thecolumn, it is possible to carry out more than 400 analyses in linewithout requiring the intervention of an operator and this according toa controlled work protocol.

[0013] The invention also has for its object a process for thepreparation of fluid specimens, in particular concentrates, byliquid/solid extraction, for line analysis in a suitable measuringsystem such as a UV spectrometer, an infrared device, a fluorimeter, aspectrometer or the like, characterized in that it consists in taking aspecimen, supplying at the selected flow rate a specimen or solvents toa column extraction device, causing to circulate by means of a directionreversing valve the specimen and/or the solvents either in onedirection, or in the other in said extraction device, collecting at theinverting valve, no matter what the direction of circulation, thetreated fluid to direct it toward a selector delivering the treatedfluid either to an analysis device or toward a rejection installation,detecting in real time and continuously the condition of wear of thecolumn (3) ensuring the extraction function and actuating, by means ofswitching valves (4), another column (3) adapted to ensure theextraction function when the active column (3) is detected as being in anon-functioning condition.

[0014] Such a process permits a reuse of each column so as to be able tocarry out more than 80 analyses in line.

[0015] The invention will be better understood from a reading of thefollowing description of embodiments, with reference to the accompanyingdrawings, in which:

[0016] FIGS. 1 to 4 represent schematically the different constituentelements of the installation and their respective positioning in thecourse of four cycles of an analysis including successively aregeneration cycle, a specimen loading cycle, a rinsing cycle and anelution cycle.

[0017] The installation for the automatic preparation of the specimensis more particularly adapted to permit the preparation of concentratesof organic compounds dissolved in a liquid phase. Such an installationis for example particularly adapted to the line analysis of specimens ofnatural or treated waters eventually destined for consumption, whosecontent in organic micro-pollutants, in particular in pesticides, mustbe controlled.

[0018] This installation comprises, in a manner known per se, a devicefor taking a liquid specimen to be analyzed, this taking device beingadapted to be constituted by a simple pump (not shown). Downstream ofthis taking device, there is provided a distribution device comprising avalve 1, preferably low pressure, capable of selecting either thespecimen, or one of the different solvents or reagents needed for theliquid/solid extraction process. In the illustrated examples, this lowpressure valve 1 comprises several inlets E₁ to E₅, each connected to asolvent or to a reagent or to the specimen, and a common central outletconnecting the distribution device to a low pressure volumetric pump 2.It is to be noted that, by low pressure, there is meant a pressure below7 bars. By way of example of a distribution device, there can be used avalve trademarked Rheodyne-Labpro valve, of the low pressure 7 passageand 6 position type.

[0019] The low pressure volumetric pump 2 itself permits supplying atthe selected flow rate a liquid/solid extraction device constituted by aplurality of columns 3 each comprising at least one adsorbent phase.Each column or adsorbent cartridge, which permits fixing and theneluting and concentrating the organic compounds, is comprised generallyof a tube of a diameter of 6.35 mm constituted by an inert materialwhich can be glass, “Teflon” (trademark) or a high density plastic. Inthe example described below, the body of the columns used is of highdensity polyethylene. This tube terminates in two fittings permittingsealed connection to the rest of the installation. The connection isdesigned to resist a pressure of several bars.

[0020] The phase used is dependent on the application. In the exampledescribed hereafter, the phase used is a polymeric compound. This phaseis maintained in the tube by two stainless steel sintered members. Thephase volume is of the order of several milliliters. In the examplegiven below, it is 0.5 ml. The sintered pieces used have a cutoffthreshold of several microns. To avoid any untimely plugging, it is thusnecessary to use specimens that have been pre-filtered to 10 μm.

[0021] In a manner characteristic of the invention, the extractiondevice comprises, on both sides of the columns 3, a valve 4 controllableto switch from one column 3 to another to place in action a column 3adapted to ensure the extraction function when another column 3 is in anon-working condition. The switching of each switching valve 4permitting the placing in operation of one column 3 adapted to ensurethe extraction function when the other column is in a non-workingcondition, is controlled by means of a plugging up detection device forthe columns 3 so as to ensure automatic operation of the extractiondevice. Thus, in this case, when one column is plugged, the installationautomatically switches to a new column 3.

[0022] The device for detecting the plugged condition of the columns canbe constituted by a device 6 for measuring pressure, such as a pressuredetector with a flush membrane. This pressure measuring device 6 can bepositioned between the low pressure pump 2 for supplying the extractiondevice, and a valve 5, which will be described hereafter, said directioninverting valve. The use of a pressure detector 6 with a flush membranepermits avoiding dead spaces. The switching pressure can be programmedaccording to the use.

[0023] In the illustrated examples, the switching valves 4 that are usedare multi-path slide valve also called a valve with n paths and n−1positions. Such valves are particularly produced by the Rheodyne: Labprocompany. They are of the 7 path, 6 position low pressure type, with a{fraction (1/16)}^(th) inch connector and are referred to as Touzart andMatignon 014.439.10. Another valve produced by Valco, Cheminert C25Z,with 6 to 10 paths, {fraction (1/16)}^(th) inch connector, calledTouzart and Matignon 136.011.30, 136.011.31, 136.011.32 could also beused.

[0024] These valves comprise, like the valve 1 of the distributiondevice, N peripheral paths connected to a column 3 and a central commonpath adapted to be connected selectively with one peripheral path. Thiscentral path is moreover connected to a direction reversing valve 5which will be described hereafter.

[0025] The presence alone of the switching valves would not suffice topermit the installation to operate in an autonomous manner over fairlylong periods of time. As a result, further to increase the period ofoperation of such an installation, it is necessary to increase thelifetime of each column. To do this, a direction reversing valve 5 isinterposed between each switching valve 4 and the low pressure pump 2.This direction reversing valve 5 is thus common to each switching valve4. This controllable direction reversing valve 5 is arranged to impressone direction of circulation of the fluid in any one of the columns 3 ofthe switched extraction device by the switching valves 4 and to ensurethe return of this fluid to the valve 5 so as then to distribute thetreated fluid toward a circuit that is selected either to put it away orto analyze it. This direction reversing valve 5 can be constituted by avalve with n paths and 2 positions, such as a low pressure Rheodyne:Labpro valve, 6 paths, 2 positions, {fraction (1/16)}^(th) inchconnector, referred to as Touzart and Matignon 014.439.12 or a Valcovalve, Cheminert C22Z, 6 to 10 paths, {fraction (1/16)}^(th) inchconnector, calleld Touzart and Matignon 136.011.16, 136.011.17,136.011.18.

[0026] The control means for the direction reversing valve 5 are subjectin operation to a cycle of operations preprogrammed as a function of thepreparation of the specimen to be carried out. Thus, as shown in thefigures, as a function of the position of the valve 5, the circulationof the fluid will take place in a first circulation direction within thecolumn 3 or according to a second circulation direction calledcountercurrent, within the column.

[0027] The installation further comprises, downstream of the directionreversing valve 5 and connected to this latter, a valve 7 called acontrollable selection valve to deliver the treated fluid either towardan analysis device 8, not shown in detail, or toward an installation 9for rejection or discard (not shown). Contrary to the switching valves4, whose control is a function of signals supplied by the detectiondevice 6, the control means for the direction reversing valve 5 and theselection valve 7 are subject in operation to a cycle of operationspre-programmed as a function of the preparation of the specimens to becarried out. However, the switching of the switching valves 4 cannottake place during the analysis of a specimen. This switching can takeplace only after the different analysis cycles have been carried out.

[0028] For the control, the installation includes a computer providedwith software permitting configuring as desired theextraction/concentration process. The software is designed to permitfree programming of each element of the system such that the operatorcan completely program his methods of concentration. The controlautomation of the system regulates a series of sequences of pumpingwhich define a concentration method. One pumping sequence is defined bya succession of switching orders for the different valves and terminateswith the end of the pumping action, which is to say the programming ofthe volume to be pumped and of the speed or time of pumping. Thesedifferent sequences are coded into a control panel according to a simplecontrol language which is then interpreted by the control software. Onemethod of concentration corresponds to one file. This control softwarealso is responsible for the control of the switching of the columns ofthe extraction device. It acquires the measurement of internal pressureof the circuit of the installation and, as a function of an adjustablethreshold, decides on the switching to a new column. This softwaredisplays the condition of the different columns. It positions anindication when the last column is switched. The frequency ofmeasurements is programmable in real time and can be controlled by anexternal computer.

[0029] Of course, all of the elements of the installation describedabove are constituted by inert material resistant to corrosive liquidswithout thereby releasing traces of organic compounds adapted tointerfere with the ultimate analysis. The materials that can be used areparticularly stainless steel, ceramics and Teflon. The hydraulicconnections between the different elements are ensured by Teflon tubes.

[0030] Thanks to such an installation, it is possible to use processesin which, after loading the specimen into the column 3, such as naturalor treated waters eventually adapted for consumption, adapted to containpesticides or other organic pollutants, said column 3 is successivelysubjected to a cycle of rinsing, a cycle of elution, then a cycle ofregeneration, the loading cycle and the rinsing cycle being operatedaccording to a first direction of circulation of the fluid in the columnwhilst the elution cycle and regeneration cycle are carried out bycountercurrent circulation of fluid in the column. The circulation ofthe fluid in the course of these cycles is shown by a wider line inFIGS. 1 to 4 which correspond respectively to the cycle of regeneration,the cycle of loading, the cycle of rinsing and the cycle of elution.

[0031] Moreover, the circuit of the installation is subjected betweeneach cycle to the actions of purging and reconditioning each deadvolume, in particular between valves.

[0032] Parallel to these cycles, there is detected in real time andcontinuously the state of wear of the column 3, ensuring the function ofextraction, and there is actuated, by means of the switching valves 4,another column 3 adapted to ensure the extraction operation when theactive column 3 is detected as being in a non-working condition.

[0033] Thus, by way of example, an operating protocol is givenhereafter. A first volume of 5 ml of methanol is placed in the column tocondition it. Then 5 ml of distilled water are placed to eliminate anytrace of solvent after concentration. These two steps (FIG. 1) arecarried out in the reverse direction of loading and at a speed of 5ml/mn. The water load (FIG. 2), corresponding to the specimen to beprepared, is carried out at 10 ml/mn. Rinsing of the column (FIG. 3) iscarried out at 5 ml/mn in the loading direction with distilled water,comprising a certain percentage of acetonitrile. This percentage canvary as a function of the compounds that are sought. Additions of acidor salt can be carried out in the case of poor retention of thecompounds. Elution of the column (FIG. 4) takes place in the reversedirection of loading at a speed of 1 ml/mn. The system is so calibratedas to retain only 1 ml of the most concentrated eluate. The regenerationof the column takes place at the same time as the step of conditioningthe column with methanol.

[0034] It is to be noted that the low pressure volumetric pump does notoperate during switching of the valves 4, 5, 7. The reprogrammable filefor each specimen preparation to be carried out contains therefore allthe information necessary for practicing such a protocol. It moreovercomprises information on the positions that are to be taken by thevalves for each cycle.

[0035] The final analysis can be carried out by UV or visiblespectrophotometry or by any other method of detection or separation fora liquid effluent, such as for example refractometry, fluorescence,electrochemistry, conductivity, radioactivity, mass spectrometry, highperformance liquid chromatography or the like. In the case of aninstallation measuring UV, there is preferably used a visible UVspectrophotometer with sweeping or with a bar of diodes provided with amulti-well system permitting the analysis of several measurement pathsprovided with wells of a diameter and an optical path of different sizesso as to be able to analyze raw waters that are loaded and an eluate oflow volume. So as to decrease the instrument noise, several consecutiveacquisitions of spectra will be carried out, the spectra being thenaveraged.

[0036] The analysis of the UV spectrum can be based on the deconvolutionmethod proposed by Professor Thomas of the School of Mines of Ales. Thismethod is integrated into the Secoman spectrophotometer in a standardmethod. The columns 3 of the mentioned installation can be used a largenumber of times. Tests that have been carried out give a number of usesof the order of 80 before overpressures appears which indicate pluggingof the column. The extraction output is very high. It is independent ofaging of the column.

1. Installation for the automatic preparation of specimens, particularlyof concentrates of organic compounds dissolved in a liquid phase, forline analysis in a suitable measuring system such as a UV spectrometer,an infrared device, a fluorimeter, a mass spectrometer or the like, thisinstallation comprising a) a device for taking a liquid specimen, b) adistribution device comprising a preferably low pressure valve (1)capable of selecting either the specimen, or one of the differentsolvents or reagents needed for a liquid/solid extraction process, c) alow pressure pump (2) permitting supplying at the selected flow rate aliquid/solid extraction device, d) a liquid/solid extraction devicecomprising several columns (3) each comprising at least one adsorbentphase, the installation being characterized in that the extractiondevice comprises, on opposite sides of the columns (3), a valve (4)controllable to switch one column (3) to another to place in action acolumn (3) adapted to ensure the extraction operation when anothercolumn (3) is in a non-working condition, each switching valve (4) beingconnected to a common direction reversing valve (5) interposed betweenthe low pressure pump (2) and the switching valves (4), thiscontrollable direction reversing valve (5) being arranged to impose adirection of circulation of the fluid in any one of the columns (3) ofthe extraction device and to ensure its return to said valve (5) todistribute the treated fluid toward a selective circuit either fordiscard, or for analysis.
 2. Installation according to claim 1,characterized in that the switching of each switching valve (4)permitting the operation of a column (3) adapted to ensure theextraction operation when another column is in a non-working condition,is controlled at least by means of a device for detecting plugging ofthe columns (3) so as to ensure automated operation of the extractiondevice.
 3. Installation according to claim 2, characterized in that thedevice for detecting the condition of plugging of the columns is apressure measuring device (6) preferably a flush membrane pressuredetector.
 4. Installation according to claim 3, characterized in thatthe pressure measuring device (6) is disposed between the low pressurepump (2) for supplying the extraction device and the direction reversingvalve (5).
 5. Installation according to one of claims 1 to 4,characterized in that it comprises, downstream of the directionreversing valve (5) and connected to this latter, a so-calledcontrollable selection valve (7) to deliver the treated fluid eithertoward an analysis device (8) or toward a rejection installation (9). 6.Installation according to claim 5, characterized in that the controlmeans of the direction reversing valve (5) are subject in operation to acycle of operations preprogrammed as a function of the preparation ofthe specimen to be carried out.
 7. Installation according to one ofclaims 1 to 6, characterized in that the switching valve (4) is amulti-path slide valve.
 8. Process for the production of fluidspecimens, in particular of concentrates by liquid/solid extraction, foranalysis in a suitable measuring system (8) such as a UV spectrometer,an infrared device, a fluorimeter, a spectrometer the like,characterized in that it consists in taking a specimen, to be suppliedat the selected flow rate as a specimen or as solvents, to an extractiondevice with columns, causing to circulate by means of a directionreversing valve (5) the specimen and/or the solvents either in onedirection or in the other direction in said extraction device,collecting at the reversing valve (5), no matter what the direction ofcirculation, the treated fluid to convey it toward a selector (7)delivering the treated fluid either toward an analysis device (8), ortoward a rejection installation (9), detecting in real time andcontinuously the condition of wear of the column (3) ensuring theextraction operation and actuating, by means of switching valves (4)another column (3) adapted to ensure the extraction operation when theactive column (3) is detected to be in a non-working condition. 9.Process according to claim 8, characterized in that after loading on thecolumn (3) the specimen such as natural or treated water is eventuallyadapted for consumption and adapted to contain pesticides or otherorganic pollutants, said column (3) is subjected successively to a cycleof rinsing, a cycle of elution then to a cycle of regeneration, theloading cycle and the rinsing cycle being operated according to a firstdirection of circulation of the fluid in the column whilst the elutioncycle and the regeneration cycle are operated by countercurrentcirculation of fluid in the column.
 10. Process according to one ofclaims 8 and 9, characterized in that between each cycle the circuit ofthe installation is subjected to purge and recondition of each deadvolume.